Đáp án:
$\begin{array}{l}
2)\\
\frac{a}{b} = \frac{c}{d} = \frac{m}{n} = \frac{{a + c}}{{b + d}} = \frac{{c + m}}{{d + n}} = \frac{{a + c + m}}{{b + d + n}}\\
3)\\
a)A = {\left( {\frac{{ - 1}}{2}} \right)^3} + {\left( {\frac{5}{6}} \right)^0} - {\left( { - \frac{3}{2}} \right)^2} - {\left( { - 1} \right)^{10}}\\
= - \frac{1}{8} + 1 - \frac{9}{4} - 1\\
= - \frac{1}{8} - \frac{9}{4}\\
= \frac{{ - 1 - 9.2}}{8} = \frac{{ - 19}}{8}\\
B = \left( { - \frac{4}{9} + \frac{3}{5}} \right):\frac{5}{6} + \left( {\frac{1}{5} + \frac{5}{9}} \right):\frac{6}{5}\\
= \frac{{ - 20 + 27}}{{45}}.\frac{6}{5} + \frac{{9 + 25}}{{45}}.\frac{5}{6}\\
= \frac{7}{{45}}.\frac{6}{5} + \frac{{34}}{{45}}.\frac{5}{6}\\
= \frac{{42}}{{225}} + \frac{{17}}{{27}}\\
= \frac{{551}}{{675}}
\end{array}$
